This invention relates generally to semiconductor integrated circuits and, particularly, to lithographic techniques for patterning and defining structures on integrated circuits.
Integrated circuits may be manufactured by processes that use lithography. Generally, lithography involves exposing a surface to create a mask on a semiconductor structure. That mask may then be utilized to form desired structures in or over the semiconductor structure.
Commonly, the mask may be defined in a photoresist that is exposed to light. Photoresist may be either positive or negative photoresist. Positive photoresist becomes more soluble when exposed and negative photoresist becomes less soluble when exposed. Thus, by exposing a photoresist through a selective light pattern, some regions of the photoresist may be exposed while others are not. As a result, the solubility of the exposed regions is different from the solubility of the unexposed regions. This difference in solubility may be utilized to create a mask on the semiconductor structure to define features therein, for example, by etching.
One issue with photolithography is that there may be reflection from the underlying semiconductor structure during exposure that alters the effectiveness of the photoresist. To overcome this problem, a bottom antireflective coating (organic bottom ARC) substrate may be utilized. In such case, the substrate is coated with an anti-reflective coating.
Organic bottom ARCs may be very difficult to completely etch using standard etch techniques, with relatively poor selectivity to photoresist and a propensity to cause defects. For example, in some cases, a portion of the bottom ARC may remain after processing. This may cause a defect in the resulting product.
Because of the relatively low selectivity to photoresist, the etching used to remove the ARC may result in higher resist erosion rates during the ARC etch. The higher erosion rates may result in poor etch profiles and micromasking defects caused by incomplete removal of the ARC during the subsequent substrate etch.
Thus, there is a need for anti-reflective coated substrates that have more readily removable anti-reflective coatings.